Good warning that Via Ferrata climbing is not “safe”.
Because even if you’re well-connected to the steel cable, you can still take a high-impact fall. Which puts a lot of stress on the safety equipment (which is not supposed to fail, but)—or a lot of stress on your body, especially spine or pelvis. Or you can hit protruding sections of rock (or protruding steel cable anchors) along the way down before you reach the bottom of your fall.

So despite the steel cable and the VF lanyard protection kit, taking a fall on a Via Ferrata is generally a very bad idea.

One problem I see is that lots of people (often with urging of friends) take on Via Ferrata routes of too high a difficulty, with the excuse that the safety equipment will save them. Better is to start with a VF route of an easier difficulty rating, find out how hard it feels.

Another problem is that people do strenuous VF routes without having a third “leash” or “longe” or “cow’s tail” lanyard - to clip to a cable anchor to rest (so this third piece is not for safety, just for resting). Without that, they keep getting more tired, run out of strength just as they’re unclipping and re-clipping one of the safety lanyards to the next section of steel cable, then take a high-impact fall.
(a refinement of this problem is that I once climbed with a partner whose leash or longe for resting was too long - which made it very strenuous to grab the cable again after resting).

Equipment ...
A solution to the danger of high-impact falls is the Skylotec Skyrider VF kit. It works so that even if you fall, you most likely will not fall any significant distance. It’s a little heavier and a little slower for re-clipping to the cable while climbing. I own one, have used it successfully several times—I carry it when I’m doing a route in a style in which I might fall).

Also: Perhaps it’s not wise to try to purchase the lightest possible VF kit. And of course if you own your own VF kit, then you know its usage history.

Yes good point.
Though not because anyone got hurt using it. Rather because something inside it sticks or “blocks” so it’s difficult to unclip + re-clip easily.

Which actually happened with mine. So now I have the newer version, which so far works fine—no sticking or blocking so far.

Seems to me that if you do think you actually might fall on a route because of its difficulty or because of the style you’re using to climb it, you ought to be using the Skylotec Skyrider.

(Myself on many VF routes when I’m using one my safer Via Ferrata climbing styles, I think based on experience climbing many many VF routes, that the chance of me falling is very very remote, so I prefer the quickness + convenience of a different VF kit.)

I have no experience with VF, but as a climber I wonder how wise it is to rent this kind of gear--you don’t know what it’s been through and the shop may not know either, if previous renters don’t tell them.

Well ... expert rock climbers routinely trust their lives to gear which is not their own, namely slings + chains + rings for abseil/rappel. And sport climbers routinely risk their bodies to trusting that the first bolt off the ground will hold a fall.

A key issue is if it is straightforward to inspect a piece of gear whose history you cannot know (which climbers often feel is true of equipment for abseil/rappel) - (but is generally not true of sport-climbing bolts).
Another factor is how “over-engineered” a piece of gear is for its use. And of course the reputation of those who manufactured and installed it.

Via Ferrata kits used to be simple and readily inspectable: e.g. the Petzl Zyper—I doubt you’d have much hesitation about using a rental Zyper if you could inspect it before leaving the shop, and you were trying your first VF route and it was of great reputation and you had every reason to believe it was well within your ability.

Then recently two major innovations: (1) “screamer” style shock absorbers replacing “rope thru holes in a plate”; (2) elasticized lanyard arms replacing simple nylon slings or rope. The second is just convenience, the first arguably improved safety especially for lighter climbers. But both make inspection by even an experienced user much more difficult.

Add to that the tremendous growth in popularity of VF drew many new manufacturers and distributors into the game—each trying to make some claim to new design feature, or lightness, or cheapness. With each new model and feature a learning curve in manufacturing, especially when the brilliant design engineers are in Europe and the factory is in China.

Add to that that many VF routes have their cable anchors positioned for best Aid, not for protection in case of a Fall, and that many VF climbers are even more clueless than novice rock climbers, and . . .

the surprising thing is that there have not been more equipment failures.

Actually maybe it’s not so surprising—since my experience is that there are very few non-short falls taken by Via Ferrata climbers. Partly because most of them nowadays climb using the less-fun style of grabbing the cable all the time with their hands. And French-style routes (as opposed to Dolomite-style) often have so many extra unnecessary steel fixtures that there’s usually something nearby to clip if a climber suddenly discover a need to rest.

The downside of this along with the current proliferation of new models of VF kits, is that no single model gets many real-world tests of high-impact falls. Pretty hard to get a statistically significant sample to distinguish whether there’s a design or manufacturing problem with a specific model, or if the model has avoided failures with serious consequences just by luck.

Maybe some manufactures will start offering a new model with “extra safety” or “high durability” as the feature-of-the-day. (As Mammut.ch has with some of its rock-climbing ropes)

The problem is that in order to be interested in that kind of design, Via Ferrata climbers first would have to accept that VF climbing is unsafe—and that would change the cultural appeal of VF as a “safe” form of rock-climbing.

Something that might surprise rock-climbers is the metal-on-metal aspect of a fall on a Via Ferrata cable. Because on many routes the fall is stopped by the karabiner at the end of the lanyard arm of the VF kit hitting against the rigid cable anchor (normally a thick steel shaft perpendicular to the surface of the rock).
A surprise to me is that I have not heard reports of carabiner failures. Perhaps one reason is that most VF climbers most of the time have two leashes each with its own karabiner attached to the cable, so even if one ‘biner breaks against the anchor shaft, the other one saves the climber.

. (Given that redundancy, it makes me wonder what actually happened in the recent case reported at the top of this page thread about VF kit equipment failure? The situation with the longest fall potential is when unclipping the first lanyard from the cable just below the next higher anchor point, with the intent of quickly re-clipping it to the cable just above that anchor point—so possibly even with best usage procedures there was only one VK kit lanyard arm attached to the cable at the moment of impact.)

Anyway some (few) modern VF routes have a conical rubber bumper on top of any of the cable anchors which might take a high-impact fall, so that the lanyard carabiner hits rubber with a well-designed shape for it, instead of a steel post which is a shape not designed to be “friendly” to an impacting ‘biner.

Other (few) modern VF routes deliberately put extra slack into the steel cable, so at the bottom of the fall, the ‘biner comes into “bight” or semi-loop at the bottom of the cable section near the anchor, to the main impact normally comes first onto the (more flexible) cable, and normally hits the rigid anchor post only after going slightly upward.

I personally like the “rubber bumper” installations—and hate the “extra slack” method because the slack cable is much more difficult (than a taut cable) for most climbers to haul themselves up on, so then the route designers add even more and larger unnecessary metal rungs and posts alongside the cable for the climbers to put their hands on and pull themselves up. All these extra fixtures make it very difficult for me to enjoy my own favorite style of climbing: which is to put my hands + feet directly on the rock as much as possible (and use the installed metal only for protection, not aid).

Equipment problems are clearly serious but I think it’s a bigger concern that people have unrealistic ideas about the risk level of via ferrata routes. The safety advice of not falling has been a bad joke for years. Swiss TV recently did a peice on how safe and fun via ferrata were which isn’t helpful. It’s also pretty clear that hire stores aren’t really able to give the guidance required before people set out.